a. Field of the Invention
The present invention pertains generally to fluid detection and, more particularly, to the use of cables for detection of the presence of fluids.
b. Background of the Invention
Cabled sensors and cables have been used in the detection of the presence of fluids. In many applications, it is desirable not only to detect the presence of fluids, but also to determine the location of a fluid.
The ruggedness and durability of the cable used is important. For example, in industrial, commercial or residential applications, movement of people or objects above or near the cables may result in breakage or disconnection of the cable. Hence, fluid detection cables need to be sufficiently rugged to minimize potential breakages or disconnections.
In some cases, placement of a structure or object near or on top of the cable may cause a malfunction of the fluid detection system either with a false detection when no fluid is present, or failure to detect a fluid when one is present. Some existing cables have a disadvantage when used around metal structures or other conductive materials since contact with conductive surfaces can form a short circuit across the sensing leads of the cables which can cause a false alarm in the fluid detection system. In existing fluid detection cables, certain conductive elements (e.g. conductors) of the cable must make contact with the fluid to detect the presence of the fluid. In some cases the construction of the cable is such that sensing leads are not disposed to immediately sense small amounts of fluid. A fluid may be present, but the level of the fluid may be too low to be in contact with the sensing leads. Hence, these cables do not detect fluids until the level of the fluid is sufficiently high.
Fluid detection cables that are too big or that have the wrong shape, may also negatively impact the site where they are installed. For example, many round fluid detection cables have a diameter of ¼ inch or more. Installation of such cables below a carpet or other floor covering creates a trip hazard or at a minimum an unsightly bump.
Another problem with previous fluid detection cables is that the size of the cable makes it difficult to install the cable in tight places. For example, in the construction of a building, it may be desirable to install fluid detection cables directly adjacent to or along the bottom of a wall or in other tight spaces. Existing cables are too large, or the wrong shape, and thus are not suitable for use.
Installation of fluid detection systems with cables into environments where equipment, floor coverings, or other structures are already in place may be difficult or impossible, due to the size and the shape of the cable, and the size and shape of the connecters.
Another problem with existing fluid detection cables is that when a leak or other contact of the cable with fluid occurs, it is necessary to dry the cable in order for the system to properly function again. Many cables are constructed with hygroscopic materials, i.e., materials that absorb moisture, or act as a wick to draw in and retain fluids. Drying of these cables to return them to the normally dry state required for fluid detection may require removal of the cable from the installed site followed by heating or blowing the cable for a period of time until the moisture has evaporated. Removal and reinstallation of the cable from an installed site may be difficult and time consuming. In some situations the cable can be dried without removing it, but the drying process is time consuming and may damage the cable by heating it. Also, some fluid detection cables require a fastener to secure the cable. Such fasteners must be placed at regular intervals. Other fluid detection cables must be glued to the floor. Such fastening of the cables with certain shapes and sizes may be necessary for proper function, but it makes removal and drying time consuming and difficult. When the cable is fastened to a surface, the use of large or expensive connectors at the ends of the cable makes cutting the connectors from the ends of the cable in order to remove it by pulling it through the fasteners difficult and costly.
Further, existing fluid detection cables and connectors require expensive materials. As a result, the cost of a fluid detection system is high, especially for residential applications or other applications requiring relatively low cost.